78 lines
5.2 KiB
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78 lines
5.2 KiB
HTML
<!-- Common Lisp HyperSpec (TM), version 7.0 generated by Kent M. Pitman on Mon, 11-Apr-2005 2:31am EDT -->
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<TITLE>CLHS: Function MAPHASH</TITLE>
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<H1><A REV=MADE HREF="http://www.lispworks.com/"><IMG WIDTH=80 HEIGHT=65 ALT="[LISPWORKS]" SRC="../Graphics/LWSmall.gif" ALIGN=Bottom></A><A REL=TOP HREF="../Front/index.htm"><IMG WIDTH=237 HEIGHT=65 ALT="[Common Lisp HyperSpec (TM)]" SRC="../Graphics/CLHS_Sm.gif" ALIGN=Bottom></A> <A REL=PREV HREF="f_remhas.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Previous]" SRC="../Graphics/Prev.gif" ALIGN=Bottom></A><A REL=UP HREF="c_hash_t.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Up]" SRC="../Graphics/Up.gif" ALIGN=Bottom></A><A REL=NEXT HREF="m_w_hash.htm"><IMG WIDTH=40 HEIGHT=40 ALT="[Next]" SRC="../Graphics/Next.gif" ALIGN=Bottom></A></H1>
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<A NAME="maphash"><I>Function</I> <B>MAPHASH</B></A> <P>
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<P><B>Syntax:</B><P>
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<P>
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<B>maphash</B> <I>function hash-table</I> => <I><A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A></I><P>
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<P>
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<P><B>Arguments and Values:</B><P>
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<P>
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<I>function</I>---a <A REL=DEFINITION HREF="26_glo_d.htm#designator"><I>designator</I></A> for a <A REL=DEFINITION HREF="26_glo_f.htm#function"><I>function</I></A> of two <A REL=DEFINITION HREF="26_glo_a.htm#argument"><I>arguments</I></A>, the <A REL=DEFINITION HREF="26_glo_k.htm#key"><I>key</I></A> and the <A REL=DEFINITION HREF="26_glo_v.htm#value"><I>value</I></A>. <P>
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<I>hash-table</I>---a <A REL=DEFINITION HREF="26_glo_h.htm#hash_table"><I>hash table</I></A>. <P>
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<P><B>Description:</B><P>
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<P>
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Iterates over all entries in the <I>hash-table</I>. For each entry, the <I>function</I> is called with two <A REL=DEFINITION HREF="26_glo_a.htm#argument"><I>arguments</I></A>--the <A REL=DEFINITION HREF="26_glo_k.htm#key"><I>key</I></A> and the <A REL=DEFINITION HREF="26_glo_v.htm#value"><I>value</I></A> of that entry. <P>
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The consequences are unspecified if any attempt is made to add or remove an entry from the <I>hash-table</I> while a <A REL=DEFINITION HREF="#maphash"><B>maphash</B></A> is in progress, with two exceptions: the <I>function</I> can use can use <A REL=DEFINITION HREF="m_setf_.htm#setf"><B>setf</B></A> of <A REL=DEFINITION HREF="f_gethas.htm#gethash"><B>gethash</B></A> to change the <A REL=DEFINITION HREF="26_glo_v.htm#value"><I>value</I></A> part of the entry currently being processed, or it can use <A REL=DEFINITION HREF="f_remhas.htm#remhash"><B>remhash</B></A> to remove that entry. <P>
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<P><B>Examples:</B><P>
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<P>
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<PRE>
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(setq table (make-hash-table)) => #<HASH-TABLE EQL 0/120 32304110>
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(dotimes (i 10) (setf (gethash i table) i)) => NIL
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(let ((sum-of-squares 0))
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(maphash #'(lambda (key val)
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(let ((square (* val val)))
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(incf sum-of-squares square)
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(setf (gethash key table) square)))
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table)
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sum-of-squares) => 285
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(hash-table-count table) => 10
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(maphash #'(lambda (key val)
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(when (oddp val) (remhash key table)))
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table) => NIL
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(hash-table-count table) => 5
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(maphash #'(lambda (k v) (print (list k v))) table)
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(0 0)
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(8 64)
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(2 4)
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(6 36)
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(4 16)
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=> NIL
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</PRE>
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</TT> <P>
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<P><B>Side Effects:</B><P>
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<P>
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None, other than any which might be done by the <I>function</I>. <P>
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<P><B>Affected By:</B> None.
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<P>
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<P><B>Exceptional Situations:</B> None.
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<P>
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<P><B>See Also:</B><P>
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<P>
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<A REL=DEFINITION HREF="m_loop.htm#loop"><B>loop</B></A>, <A REL=DEFINITION HREF="m_w_hash.htm#with-hash-table-iterator"><B>with-hash-table-iterator</B></A>, <A REL=CHILD HREF="03_f.htm">Section 3.6 (Traversal Rules and Side Effects)</A> <P>
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<P><B>Notes:</B> None.
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<P>
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<P><HR>The following <A REL=META HREF="../Front/X3J13Iss.htm">X3J13 cleanup issue</A>, <I>not part of the specification</I>, applies to this section:<P><UL><LI> <A REL=CHILD HREF="../Issues/iss240.htm">MAPPING-DESTRUCTIVE-INTERACTION:EXPLICITLY-VAGUE</A><P></UL><HR>
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